Tag: PLC

QLC can’t rely on it? PLC research and development has been put on the agenda by Toshiba

The SSDs we use use NAND Flash as the storage medium. As the storage density continues to increase, the cost becomes more and more sensitive. Because the cost of flash memory depends on the chip area, it can be stored in the same area. With more data, Flash will be more cost effective.

Therefore, with the development of technology, there are Single Level Cell (SLC), Multi Level Cell (MLC) and Triple Level Cell (TLC), and there is also a QLC that has not been widely popularized.

Some small partners may not understand the relationship between them. In SLC flash, each storage unit stores only one bit of information, which makes reading cells faster, but its unit cost is higher; MLC flash stores two storage units per memory unit. Bit information, read speed and lifetime are lower than SLC, but the price is also 2 to 4 times cheaper; TLC Flash stores 3 bits of information per memory unit, the advantage is that the cost is much lower than SLC or MLC flash, more suitable For consumer applications, to QLC Flash, each memory cell can store 4 bits of information to store more information, and the lifetime will be lower than TLC.

After QLC, in fact, 5bit MLC flash memory has been under study, referred to as PLC, it has to control 32 different voltages, which is more complicated, but at the just-opened 2019 FMS International Flash Conference, it has begun to explore PLC flash memory. Probably, it has been put on the agenda. Although there is no concrete object, it is believed that with the wide-scale popularization of QLC, the speed of PLC research and development will be further accelerated.

How much is the voltage of the PLC battery to be replaced with a new one?

Lithium battery for PLC storage, the battery should be replaced when the voltage is lower than 3V.
When the PLC user program is to remain in the RAM, the battery is used. The battery is usually a 3V or 3.6V non-rechargeable lithium battery. The battery life is usually about five years. When the battery is used for a long time, the voltage will be Falling, when it falls below enough to guarantee data in RAM, the program in RAM is lost. If the user does not have a backup program, it will be quite troublesome.
The general PLC has a battery voltage detection circuit inside. When the voltage drops to a certain level, the PLC will alarm and remind the battery to be replaced. The PLC’s instruction manual provides a way to replace the battery. Generally speaking, after the PLC is powered off, because the RAM power supply terminal of the PLC is connected with a charging capacitor, even if the battery is removed, the charging power on the capacitor is sufficient for the data in the RAM to remain for a period of time, so if the battery is removed in a short time (usually 5 minutes) Then replace the new battery, the data will not be lost.
However, the environment in which the user actually uses the PLC is different, for example, the capacity of the capacitor is reduced, and the RAM power supply circuit has
Dust, sludge, etc. form a discharge circuit, which will speed up the discharge speed of the capacitor after the PLC is powered off, thus making the time difficult to grasp. If you replace the battery while charging, you can keep the program safe. Because the power will always
There is a voltage applied to the power supply pin of the RAM chip. Of course, you should also be careful when changing, pay attention to the polarity of the battery and avoid short circuit.
It is best to power on the PLC for 15 minutes (charge the internal capacitor), power off, change the new battery within 5 minutes, and then power on it.